Inspired by communication mechanisms occurring in biological systems, molecular communication (MC) is a novel interdisciplinary paradigm in which the research areas of biotechnology, communication technology and nanotechnology converge [Hiyama, S. et al., 2005]. The rapid advances in these fields have brought about the miniaturization of mobile machines and robots down to nanometer dimensions. At this scale, a bio-inspired nanorobot (nanobot in short) is the most basic functional unit, consisting of nanoscale components, that is capable of performing specific tasks such as computing, data storing, sensing or actuation [Llatser, I. et al., 2012]. Such tasks can be executed through the capacity of receiving inputs and generating outputs, which in a molecular communication context requires transceiver capabilities, as nanobots receive information by reacting to specific molecules and broadcast information by releasing other molecules, according to predefined parameters.
To date, different MC systems have been proposed depending on the way message molecules propagate from transmitters to receivers [Pierobon, M. et al., 2010]. These systems have been categorized into three classifications: walkway-based, diffusion based and flow-based MC. For each category, several efforts have been undertaken to design systems and laboratory condition feasibility has been investigated [Hiyama, S. et al., 2010]. For walkway-based MC systems, a walkway-motor-interaction transport model has been proposed [Hiyama, S. et al., 2009]. In such systems, signal molecules are propagated over protein filaments (i.e. microtubules) via molecular motors [Hiyama, S. et al., 2007; Hiyama, S. et al., 2008 (a); Hiyama, S. et al., 2008 (b); Enomoto, A. et al., 2006]. Diffusion-based MC is achieved by encapsulating information molecules into vesicles that are emitted into a medium [Moritani, Y. et al., 2006; Moritani, Y. et al., 2007] where they subsequently propagate via diffusion or unpredicted turbulence of the medium. This approach also includes systems utilizing diffusion through gap-junctions between cells [Nakano, T. et al., 2005; Walsh, F. et al., 2010] and long range systems that are envisioned to make use of platforms such as hormones, pheromones, pollen or spores [Parcerisa Gine, L. et al., 2009]. There have also been accounts of a new group of longer range, actively propelled systems utilizing flagellated bacteria [Gregori, M. et al., 2011; Gregorim M. et al., 2010] and catalytic nanomotor [Gregori, M. et al., 2010] systems in which information is encoded in DNA plasmids and transmitted via bacteria or synthetic nanomotors. In flow based MC systems, signal molecules are released into a fluid medium where they are guided to their destination via currents or drifts. Such systems offer some of the most biologically realistic scenarios; i.e. as nanomachines can be deployed in flows which introduce a drift for the motion of signal molecules, such as in hormonal communication through the blood stream. Interestingly, even though vesicle and long range hormones, pheromones, pollen or spores systems might be applicable in flow guided MC systems, no research on physical systems employing such propagation systems has been published.
The fundamental challenge is to devise a biological nanobot platform that can combine the extraordinary characteristics of nano-transceivers with application-orientated functionality. Ultimately such a system will provide the blue print for a scalable single network system that can interconnect large numbers of nanobots to perform complex tasks.
General efforts in MC research have mainly focused on bio-inspired propagation systems and theoretical qualification thereof, whilst research on actual transceivers has been fairly limited. To date, two transceiver engineering approaches have been proposed; the construction of simplified artificial cell-like structures made of biological materials or adaptation of existing biological cells [Suda, T. et al., 2008]. In comparison, the DNA-origami platform, disclosed in WO 2012/061719 and Douglas et al. (2012), herein incorporated by reference as if fully described herein, sanctions a novel non-cell like approach to construct autonomous, logic-guided nanobots, that can be programmed to transport molecular payloads to targets.